Fair Value Measurements - Assets and Liabilities Measured on a Recurring and Nonrecurring Basis (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2016 USD ($) drilling_unit	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($) drilling_unit	Dec. 31, 2016 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset impairment charges		$ 0.0	$ 34.3
Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets - cash equivalents		1,211.6		$ 1,242.3
Derivative		0.0		6.1
Recurring Basis [Member] | Egypt, Pounds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets		2.4		4.2
Recurring Basis [Member] | Angola, Kwanza
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets		4.4
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets - cash equivalents		1,211.6		1,242.3
Derivative				0.0
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member] | Egypt, Pounds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets		2.4		4.2
Recurring Basis [Member] | Fair Value, Inputs, Level 1 [Member] | Angola, Kwanza
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets		4.4
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets - cash equivalents		0.0		0.0
Derivative				0.0
Other assets				0.0
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member] | Egypt, Pounds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets		0.0
Recurring Basis [Member] | Fair Value, Inputs, Level 2 [Member] | Angola, Kwanza
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets		0.0
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets - cash equivalents		0.0		0.0
Derivative				6.1
Other assets				$ 0.0
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member] | Egypt, Pounds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets		0.0
Recurring Basis [Member] | Fair Value, Inputs, Level 3 [Member] | Angola, Kwanza
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets		$ 0.0
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	$ 9.3		9.3
Assets, Fair Value Adjustment			34.3
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	0.0		0.0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	0.0		0.0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	$ 9.3		$ 9.3
Jack-up Rigs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Number Impaired | drilling_unit	5		5
Asset impairment charges	$ 34.3		$ 34.3